A fully automated image processing algorithm successfully detected endocardial boundaries and tag lines in tagged MR images, though epicardial boundaries required more manual intervention.
The proposed image processing hierarchy provides an effective, mostly automated method for detecting myocardial boundaries and tracking tags in cardiac MRI.
Tracking magnetic resonance tags in myocardial tissue promises to be an effective tool for the assessment of myocardial motion. The authors describe a hierarchy of image processing steps which rapidly detects both the contours of the myocardial boundaries of the left ventricle and the tags within the myocardium. The method works on both short axis and long axis images containing radial and parallel tag patterns, respectively. Left ventricular boundaries are detected by first removing the tags using morphological closing and then selecting candidate edge points. The best inner and outer boundaries are found using a dynamic program that minimizes a nonlinear combination of several local cost functions. Tags are tracked by matching a template of their expected profile using a least squares estimate. Since blood pooling, contiguous and adjacent tissue, and motion artifacts sometimes cause detection errors, a graphical user interface was developed to allow user correction of anomalous points. The authors present results on several tagged images of a human. A fully automated run generally finds the endocardial boundary and the tag lines extremely well, requiring very little manual correction. The epicardial boundary sometimes requires more intervention to obtain an acceptable result. These methods are currently being used in the analysis of cardiac strain and as a basis for the analysis of alternate tag geometries.
Guttmann et al. (1994) studied Myocardial motion assessment. Automated contour and tag detection algorithm was evaluated on Detection of endocardial and epicardial boundaries and tag lines. A fully automated image processing algorithm successfully detected endocardial boundaries and tag lines in tagged MR images, though epicardial boundaries required more manual intervention.